netfs: Change ->init_request() to return an error code

Change the request initialisation function to return an error code so that
the network filesystem can return a failure (ENOMEM, for example).

This will also allow ceph to abort a ->readahead() op if the server refuses
to give it a cap allowing local caching from within the netfslib framework
(errors aren't passed back through ->readahead(), so returning, say,
-ENOBUFS will cause the op to be aborted).

Signed-off-by: David Howells <[e-mail]>
Reviewed-by: Jeff Layton <[e-mail]>
cc: [e-mail]

Link: https://lore.kernel.org/r/[e-mail]/ # v2
Link: https://lore.kernel.org/r/[e-mail]/ # v3

fs/9p/vfs_addr.c

···
  * @rreq: The read request
  * @file: The file being read from
  */
-static void v9fs_init_request(struct netfs_io_request *rreq, struct file *file)
+static int v9fs_init_request(struct netfs_io_request *rreq, struct file *file)
 {
 	struct p9_fid *fid = file->private_data;
 
 	refcount_inc(&fid->count);
 	rreq->netfs_priv = fid;
+	return 0;
 }
 
 /**

fs/afs/file.c

···
 	return ret;
 }
 
-static void afs_init_request(struct netfs_io_request *rreq, struct file *file)
+static int afs_init_request(struct netfs_io_request *rreq, struct file *file)
 {
 	rreq->netfs_priv = key_get(afs_file_key(file));
+	return 0;
 }
 
 static bool afs_is_cache_enabled(struct inode *inode)

fs/netfs/objects.c

···
 {
 	static atomic_t debug_ids;
 	struct netfs_io_request *rreq;
+	int ret;
 
 	rreq = kzalloc(sizeof(struct netfs_io_request), GFP_KERNEL);
-	if (rreq) {
-		rreq->start	= start;
-		rreq->len	= len;
-		rreq->origin	= origin;
-		rreq->netfs_ops	= ops;
-		rreq->netfs_priv = netfs_priv;
-		rreq->mapping	= mapping;
-		rreq->inode	= file_inode(file);
-		rreq->i_size	= i_size_read(rreq->inode);
-		rreq->debug_id	= atomic_inc_return(&debug_ids);
-		INIT_LIST_HEAD(&rreq->subrequests);
-		INIT_WORK(&rreq->work, netfs_rreq_work);
-		refcount_set(&rreq->ref, 1);
-		__set_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags);
-		if (ops->init_request)
-			ops->init_request(rreq, file);
-		netfs_stat(&netfs_n_rh_rreq);
+	if (!rreq)
+		return ERR_PTR(-ENOMEM);
+
+	rreq->start	= start;
+	rreq->len	= len;
+	rreq->origin	= origin;
+	rreq->netfs_ops	= ops;
+	rreq->netfs_priv = netfs_priv;
+	rreq->mapping	= mapping;
+	rreq->inode	= file_inode(file);
+	rreq->i_size	= i_size_read(rreq->inode);
+	rreq->debug_id	= atomic_inc_return(&debug_ids);
+	INIT_LIST_HEAD(&rreq->subrequests);
+	INIT_WORK(&rreq->work, netfs_rreq_work);
+	refcount_set(&rreq->ref, 1);
+	__set_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags);
+	if (rreq->netfs_ops->init_request) {
+		ret = rreq->netfs_ops->init_request(rreq, file);
+		if (ret < 0) {
+			kfree(rreq);
+			return ERR_PTR(ret);
+		}
 	}
 
+	netfs_stat(&netfs_n_rh_rreq);
 	return rreq;
 }
 

fs/netfs/read_helper.c

···
 				   readahead_pos(ractl),
 				   readahead_length(ractl),
 				   NETFS_READAHEAD);
-	if (!rreq)
+	if (IS_ERR(rreq))
 		goto cleanup;
 
 	if (ops->begin_cache_operation) {
···
 	rreq = netfs_alloc_request(folio->mapping, file, ops, netfs_priv,
 				   folio_file_pos(folio), folio_size(folio),
 				   NETFS_READPAGE);
-	if (!rreq) {
-		if (netfs_priv)
-			ops->cleanup(folio_file_mapping(folio), netfs_priv);
-		folio_unlock(folio);
-		return -ENOMEM;
+	if (IS_ERR(rreq)) {
+		ret = PTR_ERR(rreq);
+		goto alloc_error;
 	}
 
 	if (ops->begin_cache_operation) {
···
 	}
 out:
 	netfs_put_request(rreq, false, netfs_rreq_trace_put_hold);
+	return ret;
+alloc_error:
+	if (netfs_priv)
+		ops->cleanup(folio_file_mapping(folio), netfs_priv);
+	folio_unlock(folio);
 	return ret;
 }
 EXPORT_SYMBOL(netfs_readpage);
···
 		goto have_folio_no_wait;
 	}
 
-	ret = -ENOMEM;
 	rreq = netfs_alloc_request(mapping, file, ops, netfs_priv,
 				   folio_file_pos(folio), folio_size(folio),
 				   NETFS_READ_FOR_WRITE);
-	if (!rreq)
+	if (IS_ERR(rreq)) {
+		ret = PTR_ERR(rreq);
 		goto error;
+	}
 	rreq->no_unlock_folio	= folio_index(folio);
 	__set_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags);
 	netfs_priv = NULL;

include/linux/netfs.h

···
  */
 struct netfs_request_ops {
 	bool (*is_cache_enabled)(struct inode *inode);
-	void (*init_request)(struct netfs_io_request *rreq, struct file *file);
+	int (*init_request)(struct netfs_io_request *rreq, struct file *file);
 	int (*begin_cache_operation)(struct netfs_io_request *rreq);
 	void (*expand_readahead)(struct netfs_io_request *rreq);
 	bool (*clamp_length)(struct netfs_io_subrequest *subreq);